This invention relates to a novel heat pump/refrigeration system, which uses solar energy as its primary energy source and is capable of providing the space heating and cooling requirements of a building.
The concepts of using the moderately "warm" heat (approximately 200.degree. F.+), which solar collectors can provide, to heat space and to operate absorption refrigeration units for air conditioning or refrigeration are known. In the main, attempts to exploit these concepts have used the solar collector merely to provide the energy needed to operate conventional heating and cooling equipment. In particular, solar heating has been carried out either by direct transfer of heat from a solar collector to the space to be heated via conventional pipes or ducts, or by using the solar heat to provide moderately "warm" heat to assist the evaporator of an otherwise conventional vapor compression heat pump (the solar assisted heat pump). During the last thirty years, solar cooling has relied primarily upon the concept of using solar heat as the energy supply for conventional (steady state) absorption air conditioning units.
In the known solar heating/cooling systems, it has been necessary to provide thermal storage in a separate facility, typically as sensible heat stored in a water tank or the like. Also, the solar energy has been employed merely to replace or supplement the energy normally generated in conventional heating plants or used to power cooling equipment. The typical solar powered system has thus been rather costly because it has included all of the components of conventional heating and cooling systems plus solar collectors, a thermal storage facility, and special controls. In addition, it has been necessary to install standby heating and cooling capacity to provide for periods of low insolation. This in general requires additional investment in conventional equipment, e.g., an additional furnace or a greatly oversized heat pump. It also requires that one have a secure conventional energy supply during periods of low insolation. Thus, utility connections must be maintained at a capacity sufficient to provide all the required services independently of the solar powered system. These requirements place solar energy at a disadvantage as compared with conventional energy forms, even at the current high prices of energy.
Certain aspects of the design of conventional systems are awkward. For example, whereas the supply of solar energy is inherently intermittent, all conventional heating and cooling equipment, especially vapor compression heat pumps and absorption air conditioners, are designed to operate on energy supplies which can be drawn upon continuously (e.g. electricity, gas). This however is not born of necessity, but of convenience. Thus, primitive "chemical effect" refrigeration machines (i.e., refrigeration devices in which chemical effects are exploited to replace the mechanical work required in vapor compression units) that operated on an intermittent cycle were replaced in the marketplace by steady state devices such as vapor compression refrigerators or air conditioners and chemical effect machines utilizing cycles such as the steady state ammonia absorption cycle. These latter devices could be operated continuously and were better adapted for use with the controls then available. Examples of intermittant cycle chemical effect devices are disclosed in U.S. Pat. Nos. 1,873,390; 1,910,970; 1,936,039; 2,138,686; 2,622,413; and 3,270,512.
Prior to 1940, a number of refrigeration devices using intermittent chemical effect refrigeration cycles similar to those described in the above-noted patents were produced and marketed commercially. The most famous intermittent refrigerator to have been marketed in the United States was the "Icyball" unit. This device consisted of a closed system having a pair of generally spherical chambers connected by a U-shaped tube, and containing an absorbent/absorbate pair, i.e., a refrigerant such as ammonia (absorbate) and water (absorbent). To use the Icyball unit, one heated the generator ball, which contained a concentrated ammonia solution, to drive off an ammonia rich vapor which migrated to and condensed in the condenser ball. The unit was then placed such that the condenser ball was in an ice chest and the generator ball was outside. As the water in the generator ball cooled, its affinity for ammonia greatly increased (ammonia vapor pressure decreased), and condensed ammonia boiled, extracting heat from the ice chest, and was absorbed in the solution contained in the generator ball. After the refrigerant had been reabsorbed, the "weak liquor" remaining in the condensor ball was drained to the generator ball, and the cycle could be repeated. The tube connecting the two chambers of the Icyball unit had an orifice which constrained the flow of vapor back to the generator ball during the reabsorption (refrigeration) phase of the cycle. This prolonged the refrigeration cycle.
Technological development of intermittent cycle refrigeration machines has been largely stagnant for almost forty years. However, intermittent machines are generally much simpler and less expensive than steady state machines, and since solar energy is inherently an intermittent energy supply, an intermittent machine powered by the sun should not be at a competitive disadvantage with a machine designed for steady state operation.
Waste heat generated by industrial processes has been used to power air conditioning and refrigeration systems which operate on both absorption cycles employing a liquid absorbent material and adsorption cycles employing a solid adsorbent. While these cycles operate in a fundamentally identical manner, with the former it is necessary at some point to pump residual liquid absorbent back to the chamber in the system where desorption takes place. This step is not required in the latter type of cycle since the adsorbents are typically nonvolatile materials such as silica gel, charcoal, or the like.